Recently, multimedia has become easy to obtain for people. The source of multimedia can be, for example, a television program, a movie, a video compact disk (VCD), or a digital video disk (DVD). In these sources, the images mainly fall into two categories. One is non-interlaced images, which are shown line by line, and the other is interlaced images, which are shown in alternate lines. These images are primarily decoded in accord with the MPEG-2 standard.
In the process for encoding/decoding MPEG-2 images, one general processing method is to de-interlace the contents of the interlaced film. WEAVE and BOB methods are common ways of de-interlacing. The WEAVE method merges two information fields to form a frame and the BOB method use a single information field to form a frame.
Obviously, the frame formed via the WEAVE method has more information and is clearer. The frame formed via the BOB method is vaguer and some static portions will jiggle, such as the logo of the television station.
Certainly, the WEAVE method also has drawbacks. When macro block (MB) data is interlaced, the motion portions in the frame formed via the WEAVE method usually have some flaws with comb shapes, which are called mice teeth.
To a certain extent, the advantages of these two methods can be combined. The BOB method is used to eliminate the mice teeth in the motion portions and the WEAVE method is used to make the static portions clearer. This kind of method is called motion adaptive de-interlacing.
The algorithm disclosed in U.S. Pat. No. 6,348,949 employs a data comparison method to determine the state of an area. This algorithm focuses on a series of decoded images and some images that needn't be decoded (applicable for television). Hence, the cost for realizing this method is higher and the necessary bandwidth of the memory is also higher.
Reference is made to FIG. 1, which is a block diagram of a current design for a de-interlacing system applied to a video stream. FIG. 1 includes: a MPEG-2 interlaced picture data encoder 10, an encoded compressed MPEG-2 video stream 102, a MPEG-2 de-interlacing device 104, a MPEG-2 data stream decoder 106, a MPEG-2 decoder with line average extractor 108, a line average based de-interlacing determinator 110, a line average based de-interlacing bitmap 112, a block data subset 114, decoding line average data 116, picture data 118, a de-interlacing video rendering unit using line average based de-interlacing bitmap 120 and a progressive display 122.
The MPEG-2 interlaced picture data encoder 10 is an MPEG-2 encoder, which is used for decoding the interlaced picture data according the MPEG-2 standard and passing the encoded compressed MPEG-2 video stream 102 to the MPEG-2 de-interlacing device 104. The MPEG-2 de-interlacing device 104 includes the MPEG-2 data stream decoder 106 and de-interlacing video rendering unit using line average based de-interlacing bitmap 120. The MPEG-2 data stream decoder 106 includes the MPEG-2 decoder with line average extractor 108, line average based de-interlacing determinator 110 and line average based de-interlacing bitmap 112.
The MPEG-2 decoder with line average extractor 108 generates the block data subset 114 and decoding line average data 116 during decoding and passes them to the line average based de-interlacing determinator 110. The line average based de-interlacing determinator 110 produces the line average based de-interlacing bitmap 112, which has two bits provided to indicate if each MB of a picture is a motion portion or motionless portion.
The MPEG-2 decoder with line average extractor 108 produces and passes the picture data 118 to the de-interlacing video rendering unit using line average based de-interlacing bitmap 120. Then, the processed picture is shown on the progressive display 122.
Accordingly, the conventional de-interlacing system and method mentioned above still have some drawbacks that could be improved. The present invention aims to resolve the drawbacks in the prior art.